Question

Which of the following will have least hindered rotation about carbon-carbon bond?

• A. Acetylene
• B. Hexachloroethane
• C. Ethane
• D. Ethylene

Answer 1

Answer: (C)

Rotation around the $\text{C}-\text{C}$ bond in ethylene ${\text{C}}_2{\text{H}}_4$ and acetylene ${\text{C}}_2{\text{H}}_2$ is not possible because of the presence of double and triple bond. Among ethane and hexachloroethane, ethane has the smallest sized group (H) bonded to carbons, hence there will be least hindered rotation about $\text{C}-\text{C}$ bond.